The collage is awesome but the puzzle just isn't. Great to see all the fantastic artists contribute, I could stare at this for days and still find new details.
But the puzzle has a lot of ambiguous edges that really threw me for a loop. It also would have been nice if I could lock pieces into position and easily visually distinguish ones I haven't locked. Also I didn't get the achievement when I solved it.
Edit: got it the second time :/